@material-ui/system 4.0.2 on Node.js NPM

A big thanks to the 30 contributors who made this release possible!

Here are some highlights ✨:

🐛 A second stability release after the release of v4.0.0.
💄 Add a new size="small" prop to the Chip component (#15751) @mbrookes
🐛 Fix three IE 11 issues (#15921, #15952, #15967) @eps1lon, @rupert-ong, @ryancogswell
And many more 📚 improvements.

[Box] Fix prop-types and TypeScript warnings (#15884) @eps1lon
[Breadcrumbs] Add theme props and override TypeScript definitions (#15950) @chrislambe
[Chip] Add size prop for small option (#15751) @mbrookes
[Container] Document the classes API (#15919) @divyanshutomar
[Dialog] Improve scroll=body CSS logic (#15896) @DominikSerafin
[Link] Better support of component="button" (#15863) @ianschmitz
[Popover] Convert to function component (#15623) @joshwooding
[Portal] Synchronously call onRendered (#15943) @Arlevoy
[Radio] Fix dot misalignment in IE11 (#15952) @rupert-ong
[theme] Return default value for spacing when no args provided (#15891) @mbrookes
[TrapFocus] Fix error restoring focus when activeElement is null (#15967) @ryancogswell
[core] Export useMediaQuery & useScrollTrigger in index.js (#15958) @adeelibr
[core] Migrate extend ButtonBaseProps typings (#15869) @joshwooding

[styles] Remove warning when component with no displayName is provided (#15913) @eps1lon
[styles] Fix createStyles for TypeScript v3.5 (#15990) @merceyz

[codemod] Improve theme codemod to handle destructured theme.spacing (#15916) @sviande

[docs] Add React + Material-UI + Firebase as an example project (#15915) @phoqe
[docs] Batch of fixes (#15996) @oliviertassinari
[docs] Fix a typo within pricing page layout example (#15978) @sdornan
[docs] Fix broken JSS links (#15972) @timkindberg
[docs] Fix most lighthouse a11y issues in input demos (#15780) @eps1lon
[docs] Fix typo (#15975) @rick-software
[docs] Fix wrong variable name (styles => useStyles) (#15908) @hiromoon
[docs] Icon TypeScript demos (#15965) @goldins
[docs] Improve dark mode (#15944) @eps1lon
[docs] Improve interactive performance (#15874) @eps1lon
[docs] Improve lighthouse a11y score in demos (#15901) @eps1lon
[docs] Mention Virtuoso as a possible virtualization integration (#15934) @petyosi
[docs] Migrate Grid demos to hooks (#15970) @merceyz
[docs] Migrate Hidden demos to hooks (#15989) @merceyz
[docs] SignIn -> SignUp typo (#15966) @Hatko
[docs] Update FUNDING.yml with Tidelift string (#15981) @jeffstern
[docs] Update the translations (#15991) @mbrookes
[docs] v4 Migration doc slight clean up (#15886) @mlenser
[example] Fix ssr example to work on Windows (#15949) @petervaldesii
[example] Fix theme palette value (#15977) @vaidehi27
[docs] Fix syntax error in v3 migration guide (#16010) @zhuangya
[docs] Use immediate export when there is no HOC (#16005) @merceyz

[core] Add dependency react>=16.3.0 requested by @emotion/core and react-js (#15982) @marco-silva0000
[core] Fix IE 11 crashes related to Object.assign (#15921) @eps1lon
[core] Minor fixes (#15875) @joshwooding
[core] Remove export of internal test-utils (#15895) @eps1lon
[core] Update babel-plugin-optimize-clsx (#15894) @merceyz
[core] Upgrade rollup and related plugins (#15939) @merceyz
[ci] Move static tests into separate job (#15890) @eps1lon
[core] Upgrade dependencies with esm support (#16000) @TrySound